The Grand Canyon is 277 miles long, up to 18 miles wide and attains a depth of over a mile. Nearly two billion years of Earth’s geological history have been exposed as the Colorado River and its tributaries cut their channels through layer after layer of rock while the Colorado Plateau was uplifted. Since that time, the Colorado River continued to erode and form the canyon to its present-day configuration. For thousands of years, the area has been continuously inhabited by Native Americans who built settlements within the canyon and its many caves.